1. Field of the Invention
The present invention relates to the use of precisely positioned micron-sized thermally conducting via holes in semiconductor materials to precisely and efficiently remove heat from high heat producing areas in semiconductor components/devices or chips to ambient atmosphere or a heat sink.
2. Description of Related Art
Microelectronic chips are typically thermally insulated by passivation and bulk materials, which make thermal transfer extremely inefficient. As a result, the design and operation of the microelectronic chip is adversely affected. Additionally, significant size and financial costs are associated with removing heat from high performance microelectronic chips.
Within the microelectronic chip industry, there is a continuous effort to improve operation of microelectronic chips. However, as shown in FIG. 1, there is a rather significant problem of localized high heating areas 114 among circuit components 112 for chips 110, which results from high switching frequency and/or high operating voltages or currents. The localized heating problem is typically aggravated by the use of multiple layers of thermally insulating materials 130, such as oxides and nitrides added for electrical isolation, or use of spin-on-glass (SOG) for environmental protection and packaging. In addition, heat problems can be exacerbated simply by the presence of bulk substrates 120, which are made primarily of silicon, upon which active devices, e.g., circuit components, are fabricated.
FIG. 2 illustrates a conventional method of extracting heat from a microelectronic chip 210 via external heat dissipation H. The conventional method involves adding a heat sink 250, such as metallic fins, mounted to a top surface of the chip 210. However, the problem of localized high heating areas 214 remains among the components 212, as a result of, for example, high switching frequency and/or much higher current densities. The higher current densities are a direct result of the continuing trend to put more devices or circuits into a smaller area. Multiple layers of thermally insulating material 230 are disposed between the heat sink 250 and active devices 212, which are typically manufactured upon a bulk substrate 220.
While these methods provide some thermal extraction for the entire chip, unfortunately, the methods are not very efficient and may even be totally ineffective in extracting heat from localized high heat producing areas because of the presence of multiple layers of thermally insulating materials disposed between the heat producing region and the external package and/or heat sink.
Another conventional method for reducing heat effects involves reducing the thermal budget of the microelectronic chip by imposing operational limits. However, this approach sacrifices the performance of the microelectronic chip.
Other conventional methods of extracting heat from microelectronic chips include employing micro-fluidic cooling pumps that use micro-channels to pump a coolant around the chip, as disclosed, for example, in U.S. Pat. No. 5,170,319 to Chao-Fan Chu et al. A method of extracting heat from microelectronic chips by controlled spray cooling is disclosed in U.S. Pat. No. 5,992,159 to Edwards et al. In particular, the method of Edwards involves providing a condensed vapor mist on the chip package. Unfortunately, micro-fluidic pumps, as well as the spray cooling method, are difficult to implement. Moreover, rather complex apparatuses must be fabricated and then attached thereto, but without damaging the existing microelectronic chip, which add several levels of risk of component failure, while increasing cost and overall size.
Yet another method of extracting heat from microelectronic chips is disclosed by U.S. patent application Publication Number 2003/0042006 to German et al., wherein large diameter, through-substrate heat plugs using powder injection molding are employed. While large diameter through-substrate heat plugs are generally more reliable than the above-described conventional heat extraction methods, the large diameter heat plugs generally cannot be fabricated during initial device fabrication and are unable to specifically or accurately target high heat producing areas of the microelectronic chip.